[RFC][PATCH 1/5] lib: add unpack_hex_byte()

[Mimi Zohar <zohar@linux.vnet.ibm.com>]

Since converting 2 ascii hex digits into a byte with error checks
is commonly used, we can replace multiple hex_to_bin() calls with
a single call to unpack_hex_byte().

Changelog:
- Error checking added based on Tetsuo Handa's patch.
- Moved the hex2bin code here, making it into a static inline function.
  (Andy Shevchenko's request.)

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
 include/linux/kernel.h |   21 +++++++++++++++++++++
 1 files changed, 21 insertions(+), 0 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 46ac9a5..d8ea13b 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -385,6 +385,27 @@ extern int hex_to_bin(char ch);
 extern void hex2bin(u8 *dst, const char *src, size_t count);
 
 /*
+ * unpack_hex_byte - convert 2 asii hex digits into a byte
+ * @byte: binary result
+ * @buf: ascii hexadecimal byte string
+ */
+static inline bool unpack_hex_byte(u8 *byte, const char *buf)
+{
+	int hi, lo;
+
+	hi = hex_to_bin(buf[0]);
+	if (hi < 0)
+		return false;
+
+	lo = hex_to_bin(buf[1]);
+	if (lo < 0)
+		return false;
+
+	*byte = (hi << 4) | lo;
+	return true;
+}
+
+/*
  * General tracing related utility functions - trace_printk(),
  * tracing_on/tracing_off and tracing_start()/tracing_stop
  *
-- 
1.7.3.4